odd iostat graph

Hey folks,

Earlier in the week I wrote a Munin plugin that takes the "await" and
"average queue length" fields from "iostat -x" and graphs them.

This seems rather odd to me :

http://picasaweb.google.ca/alan.mckay/Work#5380253477470243954

That is Qlen. And await looks similar

http://picasaweb.google.ca/alan.mckay/Work#5380254090296723426

This is on an IBM 3650 with the 2 main "internal" drives set up in a
mirrored config, and sdb are the 6 other drives set up in a RAID5 with
a global hot spare. (4 drives in array + 1 to make it RAID5 + global
hot spare)

We aren't seeing any performance problems on this per-se. But that
just seems like a really odd graph to me. Can anyone explain it? In
particular, how regular it is?

cheers,
-Alan

--
“Don't eat anything you've ever seen advertised on TV”
- Michael Pollan, author of "In Defense of Food"